Automatic Reindexing isn't triggered if assembly versions match but the files are missing locally

[ViktorKurtev-AE]

Describe the bug
Automatic Reindexing isn't triggered when assembly versions of the files / DB indexes match but the actual index files are missing locally. That would happen if a new container instance was created for example without an actual assembly version change (e.g. autoscaling situation). The DB assembly version would match the one in the deployed dll, but the actual index files would not be present in the container file system and automatic reindexing will not be triggered, leaving that container to throw errors when an indexing request hit it.

To Reproduce
Steps to reproduce the behavior:

1. Configure automatic reindexing.
2. Rebuild once and delete the index files manually.
3. Restart the application, you'll see the files won't be created even though the background process starts up.

Expected behavior
Automatic reindexing also triggers whenever the index files are missing locally, not just when the assembly versions differ.

Library Version
13.0.2

[kentico-ericd]

@ViktorKurtev-AE I don't believe the autoscaling feature is meant to cover this scenario. In the case of autoscaling, shouldn't the physical index files also be copied to the new container automatically?

[ViktorKurtev-AE]

Hey @kentico-ericd , thanks for the response :) I was just trying to give an example of a situation I could see needing this since I noticed it on a site of ours. I guess if you spawn a copy of an existing container instance it will have the index files along with it but if you spawn a fresh instance from the last image you generated this issue would arise.

I could see the issue happening as well on a regular standard load balanced environment as well. Let's say you spin up instance 1 - reindexing starts immediately on it. After a little while instance 2 spins up as well - at this point the Lucene Index items would have the new assembly versions on them and automatic reindexing wouldn't trigger on that instance either.

In general to me an "Automatic Reindexing" feature sounds like it should fix the index if the index is in a potentially invalid state. Assembly version being different is a good guess that things might be different but the actual files missing sounds like an even clearer indicator :)

[kentico-ericd]

@ViktorKurtev-AE True, I could see that load balancing scenario causing troubles- sort of like a race condition. I believe the feature was implemented specifically for SaaS deployments, but it does say "environments like Kentico Xperience SaaS" and deploying to a load balanced environment should be covered. I will report this to our developers to see what they have to say!